This proposal brings together basic scientists and clinical investigators in a cooperative research effort designed to expand knowledge of the in vivo function of adhesion receptors in vascular injury. The projects focus on injury after pediatric cardiopulmonary bypass as a model of neutrophil-mediated vascular damage, and the immune/inflammatory vasculitides as a contrasting model of lymphocyte- mediated vascular damage. The basic research projects proposed here will identify additional molecules essential to the inflammatory response and elucidate their in vivo mechanisms of action. The clinical and animal investigations will define the relative importance of different molecular mechanisms in the pathophysiology of leukocyte- mediated injury to the microvasculature. Project 1 examines the initial adhesive interactions that ultimately lead to extravasation of neutrophils and lymphocytes from the vasculature. A model vessel system in shear flow will be utilized with purified endothelial cell components in a phospholipid bilayer so that individual adhesive interactions of integrins (LFA-1, Mac-1, and VLA-4, selectins (CD62,ELAM-1, and LAM-1, immunoglobulin family molecules (ICAM-1, VCAM-1), and a peripheral vascular addressin can be studied in isolation, along with the effects of chemoattractant molecules. Project 2 molecularly characterizes the interaction of VLA-4 with VCAM-1 that is important in lymphocyte, monocyte, and eosinophil interaction with the endothelium, and develops unique blocking reagents for this adhesion pathway. Project 3 defines novel chemoattractants and chemoattractant receptors that function both in lymphocyte recirculation and recruitment in vascular diseases with an immune/inflammatory component. In Project 4 chimeric mice deficient in the adhesion receptors ICAM-1,ICAM-2,VCAM-1,ELAM-1, and CD18 are examined to define the in vivo function of these molecules in leukocyte emigration and injury to the vasculature, and to predict the maximal efficacy and full consequences of anti-adhesion therapy with monoclonal antibody (mAb). Project 5 compares and contrasts the adhesion molecules and chemoattractants induced in patients undergoing cardiopulmonary bypass versus those induced in patients with Kawasaki disease and other immune vasculitides, aiming to predict which molecules to target for therapeutic manipulation. Project 6 and Project 7 utilize whole animal and isolated heart models, respectively, of cardiopulmonary bypass to test the therapeutic efficacy of mAb to different adhesion receptors in clinically relevant models with hypothermia or normothermia and extracorporeal circuits. Cores provide support for mAb production, and adhesion-deficient animals. A short term goal of this project is to optimize the parameters of adhesion therapy for a clinical trial in cardiopulmonary bypass patients. The long term goals are to understand mechanisms by which adhesion molecules and chemoattractants participate in vascular injury in vivo, and to define novel targets for therapy.